The present invention relates to a process for producing transglutaminase (hereinafter referred to as xe2x80x9cTGxe2x80x9d) from microorganisms such as bacteria, molds and yeasts, and also a process for producing gelled proteins with TG thus obtained.
TG is an enzyme which catalyzes an acyl transfer reaction of a xcex3-carboxyamide group in a glutamine residue in a peptide chain. When TG reacts with ane-amino group of a lysine residue in protein as an acyl acceptor, an xcex5-(xcex3-Glu)-Lys crosslinking bond is formed in the molecule and between the molecules. When water functions as the acyl acceptor, this enzyme facilitates the deamidation reaction of a glutamine residue to form a glutamic acid residue.
TG produced by the present invention is usable for the production of a gelled protein, which is usable as a gel food, gelled cosmetic, etc. like a known TG derived from Actinomyces.
It has been known hitherto that TG is contained in various animal tissues. For example, TG is contained in the liver of a guinea pig and investigations are made thereon [Connellan et al., Journal of Biological Chemistry, Vol. 246,1093-1098 (1971)]. However, as for TG produced from microorganisms, only those produced by Actinomyces and Bacillus subtilis (M. V. Ramanujam et al., FASEB J. Vol. 4, A2321) and Myxomycetes (J. D. Klein et al., J. Bacteriol. Vol. 174, 2599 to 2605) were reported.
At present, TG produced by Actinomyces is practically used on an industrial scale [Japanese Patent Unexamined Published Application (hereinafter referred to as xe2x80x9cJ. P. KOKAIxe2x80x9d) No. Sho 64-27471].
The utilization of TG derived from animals for the industry, particularly for the production of a gelled protein, has the following defects:
(1) It is difficult to obtain a large amount of TG derived from animals at a low cost.
(2) The uses of TG are limited, since it demands calcium ion.
TG derived from Actinomyces has a defect that since the growing rate of Actinomyces microorganisms is usually lower than that of bacteria, a long culture time is necessitated, so that it results in increase of the production cost.
As for the practical use of TG derived from animals, such a use has never been expected because the calcium-demanding properties thereof limit the uses thereof and the mass production thereof at a low cost is impossible. TG derived from Actinomycetes has a lower growth rate than that from bacteria and is disadvantageous from the viewpoint of costs.
Therefore, the object of the present invention is to provide a new process for producing TG with microorganisms usually used for foods from old times at a high growth rate and at a reasonable cost.
After intensive investigations made for the purpose of solving the above-described problems, the inventors have found that specified microorganisms produce TG in the course of the culture thereof or they accumulate TG in their cells. The present invention has been completed on the basis of this finding.
Namely, the present invention provides a process for producing a transglutaminase, which comprises culturing microorganisms of any of the genus Micrococcus, Clostridium, Candida, Rhizopus and Monascus in a medium to produce the intended transglutaminase in the medium or in the cells of the microorganisms and then isolating the transglutaminase, and also a process for producing a gelled protein with the thus-obtained TG.